A plasma process is a technique essential for manufacture of semiconductor devices. With recent demands for high integration and high speed of LSI, a design rule of semiconductor devices has been finer and finer and the size of semiconductor wafers has been increased. Accordingly, there is a need for a plasma processing apparatus to cope with such fineness and increase in size.
However, parallel-plate type or inductively-coupled plasma processing apparatuses, which have been conventionally widely used, have a difficulty in processing large diameter semiconductor wafers with plasma with uniformity and at a high speed.
For the purpose of avoiding such a difficulty, attention has been paid to an RLSA® microwave plasma processing apparatus which is capable of uniformly forming a surface wave plasma with high density and at a low electron temperature.
In the RLSA® microwave plasma processing apparatus, as a microwave radiation antenna which radiates a microwave for generating the surface wave plasma, a radial line slot antenna used as a planar slot antenna having a plurality of slots formed therein in a predetermined pattern, is installed on an upper portion of a chamber. A microwave introduced from a microwave source is emitted through the antenna slots and is radiated into the chamber being in a vacuum state via a dielectric microwave transmission plate installed below the antenna slots. The surface wave plasma is generated inside the chamber by an electric field of the microwave so that a workpiece such as a semiconductor wafer or the like is processed.
In such an RLSA® microwave plasma processing apparatus, when plasma distribution is to be adjusted, there is a need to prepare a plurality of antennas having different slot shapes and patterns for any replacement, which is troublesome work.
For the purpose of avoiding this problem, there has been proposed a plasma source in which a microwave is distributed, a plurality of microwave introduction mechanisms including respective tuners for impedance-matching with the above-mentioned planar antennas are installed, and microwaves radiated therefrom are guided into the chamber and spatially composed inside the chamber.
Such spatial composition of the microwaves using the plurality of microwave introduction mechanisms individually adjusts phase and intensity of the microwaves introduced from the microwave introduction mechanisms, thereby adjusting a plasma distribution with relative ease.
In addition, there has been proposed a technique in which a plurality of microwave introduction mechanisms is arranged to achieve a uniform plasma distribution.
Furthermore, in such conventional techniques, a dielectric microwave transmission window (microwave transmission member) for each microwave introduction mechanism is installed in a ceiling wall of the chamber, and a microwave is radiated into the chamber via the microwave transmission window. However, this fails to sufficiently spread plasma in a circumferential direction. In other words, the number of the microwave radiation mechanisms has to be increased in order to achieve uniform plasma distribution.